[PATCH 6.4 613/800] f2fs: fix to avoid NULL pointer dereference f2fs_write_end_io()

Greg Kroah-Hartman
2023-07-16T20:21:32Z

From: Chao Yu <chao@kernel.org>

[ Upstream commit d8189834d4348ae608083e1f1f53792cfcc2a9bc ]

butt3rflyh4ck reports a bug as below:

When a thread always calls F2FS_IOC_RESIZE_FS to resize fs, if resize fs is
failed, f2fs kernel thread would invoke callback function to update f2fs io
info, it would call f2fs_write_end_io and may trigger null-ptr-deref in
NODE_MAPPING.

general protection fault, probably for non-canonical address
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
RIP: 0010:NODE_MAPPING fs/f2fs/f2fs.h:1972 [inline]
RIP: 0010:f2fs_write_end_io+0x727/0x1050 fs/f2fs/data.c:370
<TASK>
bio_endio+0x5af/0x6c0 block/bio.c:1608
req_bio_endio block/blk-mq.c:761 [inline]
blk_update_request+0x5cc/0x1690 block/blk-mq.c:906
blk_mq_end_request+0x59/0x4c0 block/blk-mq.c:1023
lo_complete_rq+0x1c6/0x280 drivers/block/loop.c:370
blk_complete_reqs+0xad/0xe0 block/blk-mq.c:1101
__do_softirq+0x1d4/0x8ef kernel/softirq.c:571
run_ksoftirqd kernel/softirq.c:939 [inline]
run_ksoftirqd+0x31/0x60 kernel/softirq.c:931
smpboot_thread_fn+0x659/0x9e0 kernel/smpboot.c:164
kthread+0x33e/0x440 kernel/kthread.c:379
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

The root cause is below race case can cause leaving dirty metadata
in f2fs after filesystem is remount as ro:

Thread A Thread B
- f2fs_ioc_resize_fs
- f2fs_readonly --- return false
- f2fs_resize_fs
- f2fs_remount
- write_checkpoint
- set f2fs as ro
- free_segment_range
- update meta_inode's data

Then, if f2fs_put_super() fails to write_checkpoint due to readonly
status, and meta_inode's dirty data will be writebacked after node_inode
is put, finally, f2fs_write_end_io will access NULL pointer on
sbi->node_inode.

Thread A IRQ context
- f2fs_put_super
- write_checkpoint fails
- iput(node_inode)
- node_inode = NULL
- iput(meta_inode)
- write_inode_now
- f2fs_write_meta_page
- f2fs_write_end_io
- NODE_MAPPING(sbi)
: access NULL pointer on node_inode

Fixes: b4b10061ef98 ("f2fs: refactor resize_fs to avoid meta updates in progress")
Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Closes: https://lore.kernel.org/r/1684480657-2375-1-git-send-email-yangtiezhu@loongson.cn
Tested-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/f2fs.h | 2 +-
fs/f2fs/file.c | 2 +-
fs/f2fs/gc.c | 21 ++++++++++++++++++---
3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d211ee89c1586..25999ed2c4258 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3815,7 +3815,7 @@ void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi);
block_t f2fs_start_bidx_of_node(unsigned int node_ofs, struct inode *inode);
int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control);
void f2fs_build_gc_manager(struct f2fs_sb_info *sbi);
-int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count);
+int f2fs_resize_fs(struct file *filp, __u64 block_count);
int __init f2fs_create_garbage_collection_cache(void);
void f2fs_destroy_garbage_collection_cache(void);
/* victim selection function for cleaning and SSR */
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index fa50c6475876c..7482af51ab408 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3284,7 +3284,7 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
sizeof(block_count)))
return -EFAULT;

- return f2fs_resize_fs(sbi, block_count);
+ return f2fs_resize_fs(filp, block_count);
}

static int f2fs_ioc_enable_verity(struct file *filp, unsigned long arg)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 61c5f9d26018e..48cb4700ba3f5 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -2099,8 +2099,9 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
}
}

-int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
+int f2fs_resize_fs(struct file *filp, __u64 block_count)
{
+ struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
__u64 old_block_count, shrunk_blocks;
struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
unsigned int secs;
@@ -2138,12 +2139,18 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
return -EINVAL;
}

+ err = mnt_want_write_file(filp);
+ if (err)
+ return err;
+
shrunk_blocks = old_block_count - block_count;
secs = div_u64(shrunk_blocks, BLKS_PER_SEC(sbi));

/* stop other GC */
- if (!f2fs_down_write_trylock(&sbi->gc_lock))
- return -EAGAIN;
+ if (!f2fs_down_write_trylock(&sbi->gc_lock)) {
+ err = -EAGAIN;
+ goto out_drop_write;
+ }

/* stop CP to protect MAIN_SEC in free_segment_range */
f2fs_lock_op(sbi);
@@ -2163,10 +2170,18 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
out_unlock:
f2fs_unlock_op(sbi);
f2fs_up_write(&sbi->gc_lock);
+out_drop_write:
+ mnt_drop_write_file(filp);
if (err)
return err;

freeze_super(sbi->sb);
+
+ if (f2fs_readonly(sbi->sb)) {
+ thaw_super(sbi->sb);
+ return -EROFS;
+ }
+
f2fs_down_write(&sbi->gc_lock);
f2fs_down_write(&sbi->cp_global_sem);

--
2.39.2